In conventional RAID controllers in conjunction with a host computer system, a disk drive sizing file is located on the host computer to which the RAID controller is connected. The file is used by a configuration tool running on the host to artificially reduce the physical capacity of all the disk drives identified in the drive sizing file. This artificial size reduction has the benefit of allowing drives with similar sizes to appear as the same size and therefore allowing the drives which may not have identical storage capacities or sizes to appear to have the same capacity or size and therefore better serve as spares for a broader range of disk drives. For example, the Global Array Manager or GAM (made by Mylex of Fremont Calif.), the RAlDfx (made by Mylex of Fremont, Calif.) and DACCF (made by Mylex of Fremont, Calif.) configuration tools, all use this method for drive sizing although the drive sizing files have somewhat different formats.
While this conventional manner of disk drive sizing provides the aforementioned functionality, the conventional method and structure have several problems, disadvantages, and limitations. First, the Drive Sizing File must be edited, by hand, properly, whenever a new type or model of disk drive is added to the computer system. The drive information that is added to the drive sizing File typically includes the disk drive vendor, model, version and the artificial size. This information must be typed into the file in precisely the right place and in precisely the right format, or it will be misinterpreted and cause serious problems. The vendor model and version information may typically be taken from an inquiry command's data retrieved from the particular new drive.
A second problem is that the artificial size values for each disk drive entered in the drive sizing file must be coordinated to match among all the like sized drives.
A third problem relates to the use of wildcard entries which may be permitted in certain of the drive sizing file fields. Even though wildcards may typically be allowed in some fields of the drive sizing file, it is still easy to make a mistake in the placement of the wildcard character or the non-wildcard characters that goes undetected. Entry and correction of actual parameters, or of wildcard characters or parameters, therefore remains a high risk operation, since erroneous entry or erroneous correction of a prior error might require a reconfiguration of possibly the entire controller.
A fourth problem or limitations is that because the drive sizing file is stored on the host computer, the conventional method involves a manual operation to update the drive sizing file onto each host computer system. Some Drive Sizing Files have thirty or more entries. The added work involved with entering and/or modifying the drive sizing file for large sites or for a user having multiple sites imposes undesirable maintenance to enter, modify, update, and/or maintain the drive sizing files.
A fifth limitation of some, but not all, configuration tools, including for example, the GAM configuration tool, is that they require the host computer system to be rebooted in order for changes in the Drive Sizing File to take effect. This is a severe maintenance problem for users and involves host down time during which the system and the data stored on the system is unavailable to users.
A sixth problem with the conventional drive sizing file method is that some controllers, such as certain Mylex External Products Division controllers and controllers made by others, cannot use a drive sizing file of conventional type. For example, the Mylex DAC9605X controllers' local configuration tool, accessed via an LCD front panel on the controller enclosure, does not and cannot take advantage of the Drive Sizing File, and it is not possible to add a new, differently sized type of drive into an array via the front panel configuration tool and have its size be artificially reduced.
Finally, it is noted that although some of the problems associated with conventional methodology may be circumvented, such circumvention where possible, requires expert user interaction to properly use a new drive type and enter its sizing data.
For these and other reasons, there remains a need for a new structure and method for sizing or resizing disk drives generally, and in particular in the environment of disk drives connected in an array, such as in a Redundant Array of Independent Disk (RAID) controller.